The present invention generally relates to implantable stimulator systems and methods, and more particularly relates to implantable stimulator systems and methods utilizing one or more implantable microstimulators for treating headache and/or facial pain.
The public health significance of headache and facial pain is often overlooked, probably because of their episodic nature and the lack of mortality attributed to them. Headache and facial pain disorders are, however, often incapacitating, with considerable impact on social activities and work, and may lead to significant consumption of drugs.
The International Headache Society (IHS) published xe2x80x9cClassification and Diagnostic Criteria for Headache Disorders, Cranial Neuralgias and Facial Painxe2x80x9d in 1988. IHS identified 13 different general groupings of headache, given below in Table 1.1.
The IHS classification of the most common types of headache is summarized in Table 2, below.
The IHS classification provides diagnostic criteria for migraine without and with aura, summarized in Tables 3 and 4 below.
The IHS classification includes several different types of migraine variants. Basilar migraine is defined as a migraine with an aura involving the brainstem. Symptoms include ataxia, dysarthria, vertigo, tinnitus and/or changes in consciousness and cognition. Ophthalmoplegic migraine is associated with acute attacks of third nerve palsy with accompanying dilation of the pupil. In this setting, the differential diagnosis includes an intracranial aneurysm or chronic sinusitis complicated by a mucocele. The ophthalmoplegia can last from hours to months. Hemiplegic migraine is distinguished by the accompanying hemiplegia, which can be part of the aura, or the headache may precede the onset of hemiplegia. Hemiplegic migraine can be familial and may last for days or weeks, clinically simulating a stroke. An additional differential diagnosis includes focal seizures.
Status migrainosus describes a migraine lasting longer than 72 hours with intractable debilitating pain, and typically occurs in a setting of inappropriate and prolonged use of abortive anti-migraine drugs. These patients may require hospitalization, both for pain control, detoxification from the abused drugs, and treatment of dehydration resulting from prolonged nausea and vomiting.
A migraine prevalence survey of American households was conducted in 1992, and included 20,468 respondents 12-80 years of age. Using a self-administered questionnaire based on modified IHS criteria; 17.6% of females and 5.7% of males were found to have one or more migraine headaches per year. A projection to the total US population suggests that 8.7 million females and 2.6 million males suffer from migraine headache with moderate to severe disability. Of these, 3.4 million females and 1.1 million males experience one or more attacks per month. Prevalence is highest between the ages of 25 and 55, during the peak productive years.
Based on published data, the Baltimore County Migraine Study, MEDSTAT""s MarketScan medical claims data set, and statistics from the Census Bureau and the Bureau of Labor Statistics, it has been estimated that migraineurs require 3.8 bed rest days for men and 5.6 days for women each year, resulting in a total of 112 million bedridden days. Migraine costs American employers about $13 billion a year because of missed workdays and impaired work function; close to $8 billion is directly due to missed workdays. Patients of both sexes aged 30 to 49 years incurred higher indirect costs compared with younger or older employed patients. Annual direct medical costs for migraine care are about $1 billion, with about $100 spent per diagnosed patient. Physician office visits account for about 60% of all costs; in contrast, emergency department visits contribute less than 1% of the direct costs.
The diagnostic criteria for tension-type headaches are summarized in Table 5, below. However, migraine symptoms may overlap considerably with that of tension-type headaches. Tension-type headaches are believed by some experts to be a mild variant of migraine headache. Patients with tension-type headaches who also have migraines may experience nausea and vomiting with a tension headache, though when they do, it typically is mild and for a shorter duration compared to that with a migraine. Tension-type headache may be a disorder unto itself in individuals who do not have migraines, and may manifest as attacks of mild migraine in individuals with migraines.
Based on a telephone survey of 13,345 people, the 1-year period prevalence of episodic tension-type headache (ETTH) is estimated to be 38.3%, according to IHS criteria. Women had a higher 1-year ETTH prevalence than men in all age, race, and education groups, with an overall prevalence ratio of 1.16. Prevalence peaked in the 30- to 39-year-old age group in both men (42.3%) and women (46.9%). Prevalence increased with increasing educational levels in both sexes, reaching a peak in subjects with graduate school educations of 48.5% for men and 48.9% for women. Of subjects with ETTH, 8.3% reported lost workdays because of their headaches, while 43.6% reported decreased effectiveness at work, home, or school.
Chronic tension-type headache (CTTH) is a subtype of tension headaches, with patients experiencing headaches daily or almost every day. In practice, the term xe2x80x9cchronic daily headachexe2x80x9d is commonly used to describe headaches lasting for greater than 4 hours per day and for at least 15 days per month. The classification of chronic daily headaches is summarized below in Table 6.
In the study of 13,345 people cited above, the 1-year period prevalence of chronic tension-type headache (CTTH) was estimated to be 2.2%. This prevalence was higher in women and declined with increasing education. Subjects with CTTH reported more lost workdays (mean of 27.4 days vs. 8.9 days for those reporting lost workdays) and reduced-effectiveness days (mean of 20.4 vs. 5.0 days for those reporting reduced effectiveness) compared with subjects with ETTH.
Chronic daily headaches are best conceptualized as an umbrella category term, referring to a group of headache disorders characterized by headaches which occur greater than 15 days per month, with an average untreated duration of greater than 4 hours per day. There are many secondary causes of chronic daily headache, including post-traumatic headache, arteritis, intracranial mass lesions, etc. There are also short-lived primary headache disorders that occur greater than 15 days per month, such as chronic cluster headache or the paroxysmal hemicranias. These secondary and short-lived disorders are outside the scope of this discussion. The most common primary, chronic daily headache disorders include transformed migraine, chronic tension-type headaches, new daily persistent headache, or hemicrania continua. Each of these diagnoses can be complicated by medication overuse (e.g., barbiturates, acetaminophen, aspirin, caffeine, ergotamine tartrate and opioids). When used daily, all of these medications can lead to a vicious cycle of rebound headaches.
The 1988 IHS classification system recognized the uniqueness of cluster headache as a clinical and epidemiological entity. Formerly classified as a vascular migraine variant, cluster headache (a.k.a. suicide headache) is thought to be one of the most severe headache syndromes. It is characterized by attacks of severe pain, generally unilateral and orbital and lasting 15 minutes to 3 hours, with one or more symptoms such as unilateral rhinorrhea, nasal congestion, lacrimation, and conjunctival injection. In most patients, headaches occur in episodes, generally with a regular time pattern. These xe2x80x9ccluster periodsxe2x80x9d last for weeks to months, separated by periods of remission lasting months to years. It primarily affects men, and in many cases, patients have distinguishing facial, body, and psychological features. Several factors may precipitate cluster headaches, including histamine, nitroglycerin, alcohol, transition from rapid eye movement (REM) to non-REM sleep, circadian periodicity, environmental alterations, and change in the level of physical, emotional, or mental activity. The IHS classification system gives specific diagnostic criteria for cluster headache, as given in Table 7 below.
The estimated prevalence of cluster headache is 69 cases per 100,000 people. Men are affected more commonly than women in a proportion of 6:1. Although most patients begin experiencing headache between the ages of 20 and 50 years (mean of 30 years), the syndrome may begin as early as the first decade and as late as the eighth decade.
Cervicogenic headache (CEH) is a headache with its origin in the neck area. The source of pain is in structures around the neck that have been damaged. These structures can include joints, ligaments, muscles, and cervical discs, all of which have complex nerve endings. When these structures are damaged, the nerve endings send pain signals up the pathway from the upper nerves of the neck to the brainstem. These nerve fibers may synapse in the same brainstem nuclei as the nerve fibers of the trigeminal nerve. Since the trigeminal nerve is responsible for the perception of head pain, the patient experiences the symptoms of headache and/or facial pain.
While many patients who are diagnosed with CEH have the traditional symptoms of tension-type headache, some of the patients who have the traditional symptoms of migraine and cluster headache also respond to CEH diagnosis and treatment.
Facial pain may be due to a number of underlying disorders. Among the most common is Trigeminal Neuralgia (also known as tic douloureux). More than 50,000 people in the US suffer from trigeminal neuralgia. It is a disorder of the trigeminal nerve that causes episodes of intense, stabbing, electric shock-like pain in the areas of the face where the branches of the nerve are distributedxe2x80x94lips, eyes, nose, scalp, forehead, upper jaw, and lower jaw. A less common form of the disorder, Atypical Trigeminal Neuralgia, may cause less intense, constant, dull burning or aching pain, sometimes with occasional electric shock-like stabs. Both forms of the disorder most often affect one side of the face, but some patients experience pain at different times on both sides. Onset of symptoms occurs most often after age 50, and it affects women more often than men. For patients with this disorder, an ordinary touch of the face, such as when brushing teeth or applying makeup, can trigger an attack. Trigeminal neuralgia is believed to be due to hyper-excitability of fibers of the trigeminal nerve or its ganglion. Microelectrode recordings from the trigeminal ganglion have demonstrated sustained high-frequency bursts during pain episodes of trigeminal neuralgia.
Trigeminal neuralgia may be treated medically with drugs that decrease neural excitability, e.g., carbamazepine or phenytoin. Such medications prove ineffective for many patients over the course of the disease. Thus, a number of surgical interventions (e.g., microvascular decompression of the trigeminal ganglion or it nerve fibers, radio-frequency rhizotomy) have been developed.
Another cause of facial pain is Temporomandibular Joint (TMJ) Dysfunction Syndrome. Most TMJ discomfort is temporary and can be treated with inexpensive remedies. However, some TMJ dysfunction patients are afflicted with persistent and sometimes unbearable pain. The symptoms of this chronic dysfunction include persistent pain in the facial muscles on one or both sides, a clicking or popping sensation when opening the mouth or working the jaw, recurring headaches, and difficulty chewing. Analgesics and anti-inflammatory medication may relieve the pain in some patients, and others turn to TMJ surgery in desperation.
Yet another cause of facial pain is Postherpetic Neuralgia, which is a possible complication of herpes zoster reactivation (xe2x80x9cShinglesxe2x80x9d). Shingles is a painful disease caused by reactivation of the herpes zoster virus (which causes chicken pox upon initial infection). It can affect the torso or limbs (spinal ganglia shingles) or the face (trigeminal ganglia shingles). Approximately one in five adults develops shingles, usually after age 50. For most people, shingles is an acute condition with pain typically lasting one month. However, in older patients or patients with a compromised immune system, postherpetic neuralgia, a very painful chronic condition, may develop. The incidence of postherpetic neuralgia is almost negligible before age 50, but at least 50% of patients older than 60 years and almost 75% beyond age 70 become affected following a shingles attack. Postherpetic neuralgia tends to improve over time without treatment. Some estimates suggest that only 2%-3% of patients have pain lasting more than one year. However, since more than 60,000 new cases develop annually in the US, the collective morbidity is still substantial. Treatment of postherpetic neuralgia consists of symptomatic relief of severe pain with tricyclic antidepressants and opioids.
The invention disclosed and claimed herein provides means for chronically stimulating a trigeminal ganglion or ganglia, a trigeminal nerve(s), or branch(es) of a trigeminal nerve(s) with a miniature implantable neurostimulator that can be implanted with a minimal surgical procedure. This invention also provides means for chronically stimulating any nerve(s) arising from the upper cervical spine (i.e., C1-C4), including a greater occipital nerve(s), a lesser occipital nerve(s), a third occipital nerve(s), a great auricular nerve(s), a transverse cervical nerve(s), a supraclavicular nerve(s), or a branch(es) of any of these neural structures with a miniature implantable neurostimulator that can be implanted with a minimal surgical procedure. Electrical stimulation of such targets may provide significant therapeutic benefit in the management of migraine, tension-type headache, cluster headache, cervicogenic headache, other types of headache, and/or facial pain.
To treat migraine, tension-type headache, cluster headache, cervicogenic headache, other types of headache, and/or facial pain, a miniature implantable neurostimulator, such as a Bionic Neuron (also referred to as a BION(trademark) microstimulator) may be implanted via a minimal surgical procedure (e.g., injection or small incision) adjacent to a trigeminal ganglion or ganglia, a trigeminal nerve(s), a branch(es) of a trigeminal nerve(s) (e.g., an ophthalmic nerve(s), a maxillary nerve(s), and/or a mandibular nerve(s)), or a branch(es) of any of these neural structures. A BION may additionally or alternatively be implanted adjacent to any nerve(s) arising from the upper cervical spine (i.e., C1-C4), including a greater occipital nerve(s), a lesser occipital nerve(s), a third occipital nerve(s), a great auricular nerve(s), a transverse cervical nerve(s), a supraclavicular nerve(s), or a branch(es) of any of these neural structures to treat migraine, tension-type headache, cluster headache, cervicogenic headache, other types of headache, and facial pain.
A microstimulator may be implanted via injection and/or via endoscopic means. A more complicated surgical procedure may be required for sufficient access to a particular nerve (e.g., a nerve surrounded by scar tissue) or for purposes of fixing the neurostimulator in place. A single microstimulator may be implanted, or two or more microstimulators may be implanted to achieve greater stimulation of one or more nerves.
The microstimulator used with the present invention possesses one or more of the following properties, among others:
at least two electrodes for applying stimulating current to surrounding tissue;
electronic and/or mechanical components encapsulated in a hermetic package made from biocompatible material(s);
an electrical coil or other means of receiving energy and/or information inside the package, which receives power and/or data by inductive or radio-frequency (RF) coupling to a transmitting coil placed outside the body, thus avoiding the need for electrical leads to connect devices to a central implanted or external controller;
means for receiving and/or transmitting signals via telemetry;
means for receiving and/or storing electrical power within the microstimulator; and
a form factor making the microstimulator implantable via a minimal surgical procedure.
A microstimulator may operate independently, or in a coordinated manner with other implanted devices, or with external devices. For instance, a microstimulator may incorporate means for sensing a patient""s condition, which it may then use to control stimulation parameters in a closed loop manner. The sensing and stimulating means may be incorporated into a single microstimulator, or a sensing means may communicate sensed information to at least one microstimulator with stimulating means.